HA Sprinkler Interface Project



For those looking to interface their sprinklers to their HA system, I've recently released a new project for doing just that. It's a DIY kit that can be built to support anywhere from 1 to 27 watering zones as well as controlling an optional irrigation/well pump. All valves are controller via opto-isolated SSR (Solid State Relays -- no coils) so there is no nasty induction/EMI problems that could crash/damage/scramble your controller then the valves open/close.

The board takes a series of requests, sent over a RS232 serial line like "water zone 4 for 20 minutes, then zone 0 for 10 minutes, then zone 7 for 45 minutes, etc". The controller then makes sure each request runs in turn to completion. So that means you need something (computer, HA controller, etc) to actually schedule the time of day stuff (i.e. 6AM send requests to start watering), but the controller can interface with sprinkler module for a few seconds and let it manage the rest of the watering process.

It can hold up to 48 watering requests at any one time and if you need them, support multiple request/watering queues (up to 8, meaning if you need it, you could have up to 8 valves open at once (or lless)). Most systems need only one queue.

There are a number of safeguards in software and hardware to make sure the unit doesn't lock up and leave your valves open all weekend. In addition to a very small valve control loop (simple == less chance for bugs), there is a hardware watchdog timer, a voltage monitor and an entirely independent supervisory program all looking for problems with the hardware or unforseen bugs in the firmware. Anything bad happens (program locks up, hardware locks up, power fluctuates, etc), the board will shutdown and close all valves. There is also automatic throttling of valve opening, so if you have >1 valve opening at the same time (which could overload your power supply), it'll stage them with a few second delay to minimze iimpact on the power supply. If you have an irrigation/well pump, there are safeties to prevent the pump from being cycled on and off too fast (i.e. short cycling).

The firmware is upgradable in place over the serial line. While you can just send simple requests to it and be done with it, the controller does support extensive reporting and status monitoring as well as the ability to alter the contents of the queues (delete entry, reorder the queue, etc) if you'd like to use it. You can ignore it all if you don't need that, so there is no additional complexity.

You put the controller wherever your valve wiring is and then run a 2 or 3 conductor cable back to your controller. I built all the controllers (mine, brothers and engihbor) on 4x6" perfboard. The 10 zone controller took about 1 hours to assemble and cost me $70USD in parts. The 27 zone one took about 3 hours to assemble and cost about $160USD in parts.

All project materials are free for non-commercial use. The schematics, precompiled firmware and firmware source code, parts lists, documentation, etc are part of the download. There is a Java GUI interface for testing/experimenting with the board and an xPL gateway module allowing integration into an xPL HA network. The underlying xPL engine (xPL4Java -- http://www.xpl4java.org) has a scheduler module being released soon with GUI, allowing, if you want, to schedule all watering via a GUI from anywhere on your network (though most folks will hook into the dedicated HA controller).

You can read more about it at http://www.rgbled.org

If you have any questions, you can post messages at the sites forums or here (I've obviously just joined, after "meaning to do it" for a while :)